Panoramic camera



ge QEFFRFNCF A. BOUWERS PANORAMIC CAMERA July 17, 1962 2 Sheets-Sheet 1Original Filed Nov. 13, 1956 FIG.2

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v KL I BERT BUUW ERS United States Patent 3,044,379 PANORAMIC CAMERAAlbert Bouwers, The Hague, Netherlands, assignor to Optische Industriede Oude Delft, Delft, Netheran s Original application Nov. 13, 1956,Ser. No. 621,794, now Patent No. 2,923,220, dated Feb. 2, 1960. Dividedand this application Dec. 7, 1959, Ser. No. 857,752 Claims priority,application Netherlands June 4, 1956 Claims. (Cl. 95-16) This is adivisional application from my copending patent application Ser. No.621,794, filed November 13, 1956, now Patent No. 2,923,220.

The invention relates to a panoramic camera, i.e. a camera whose fieldof view in one direction is considerably larger than the field of viewin the direction perpendicular thereto.

For the photographing of pictures one dimension of which is much largerthan the other (panoramas), various methods are conceivable and have infact found practical application. In one of these methods use is made ofa camera lens which, during the taking of the photograph, is moved by adriving mechanism along a stationary strip of film. Another methodconsists fundamentally in using a number of separate cameras mountedside by side, each of which covers its own particular portion of thetotal angular field desired. With these cameras, photographs are takensimultaneously which, when placed alongside each other, form thepanoramic picture.

However, the two methods mentioned, in common with other knownprocedures, entail the drawback that the apparatus used is expensive andunwieldy.

The invention aims at providing a camera of the type indicated whichcovers in one direction a field up to 360 and which takes the photographin one single exposure with a single, stationary optical system, usingstandard perforated or unperforated film.

According to the invention a panoramic camera has an optical system inthe form of a portion of a transparent sphere which has one or moreinternal retracting surfaces concentric with the external surface of thesphere. The camera housing has a partition dividing the interior into anupper and a lower compartment. The partition fits around the opticalsystem and defines thereon a light entrance area in the uppercompartment and a light exit area in the lower compartment. Light rayswithin the angular field envisaged traverse the optical system inbroadly radial directions and are focused on a film which is positionedon a transparent annular or partly annular film carrier in the lowercompartment which surrounds the optical system. In order to limit theaperture of the optical system in the plane of the large field angle, astop means is provided in front of the entrance area which is capable toprevent light rays having an angle of incidence exceeding a given value,from entering.

The optical system used in the camera has an image surface which, likeall the concentric surfaces in the system, is spherically curved in sucha way that the centre of the optical system is also the centre of theimage surface.

As the vertical dimension of the panoramic image is considerably smallerthan the horizontal dimension, in many cases a cylindrical surface willconstitute a sufiicient approximation to the exact shape of the imagesurface. The film carrier thus may assume the simple form of acylindrically curved shell of transparent material against which thefilm can be placed. However, if very high standards are stipulated forthe resolving power of the optical system, the above-mentionedapproximation as to the shape of the film support is no longer possibleand one has to use a spherically curved film carrier around which thefilm is stretched. This is not a serious drawback in practice, as thedeviations from the cylindrical shape will in any case be very slight.

However, according to the invention an advantage may be gained byoptically distorting the image surface to a purely cylindrical surface,which is achieved by interposing between the optical system and the filmcarrier coaxially with the film carrier, a cylindrically curved,transparent body whose surface facing the optical system and/ or whosesurface facing the film support is/are concavetoric in form. Thisbodywhich, for brevitys sake, will hereinafter be designated as theimage-flattening lensthus serves to lengthen the optical path of thelight-rays which will form the edge portions of the image (consideredwith respect to the shortest dimension of the image) by such an amountwith respect to the rays corresponding to the middle portion of theimage that all points in the image will be situated at substantiallyequal distances from the axis of the film carrier.

According to the invention it is expedient for the image flattening lensto be so shaped that only its inner surface is toric in form, whilst theouter surface is given a cylindrical form enabling it to be used as filmcarriers. In this way the image flattening lens is situated at theshortest possible distance from the image surface, with the result thatany aberrations introduced by this lens will have little effect on imagequality. Moreover, for the same reason the toric inner surface of thelens need not be made with very great precision.

The flattening lens may, for instance, be ground and polished on alathe.

In the invention the limitation of the aperture of the optical system tothe desired value will preferably be effected by a form of stop devicesuch that, except for slight variations, this aperture is the same forevery point on the image surface. A very simple and neat solution of theaperture limiting problem is provided if the diaphragm is situated infront of the entrance surface of the optical system and comprises aplurality of thin, opaque, flat plates evenly distributed over theentrance surface, said plates being in planes substantially radial withrespect to the axis of the film carrier. The aperture for the beams oflight entering the optical system is limited in the direction of theirwidths by these plates, a portion of the lightrays in these beams, notentering the camera radially, being intercepted by the plates. Each stopplate thus gives a shadow for each direction of the incident light, theeffect being such that shadows of adjacent plates overlap in the case ofa direction deviating from the radial by more than a certain angle. Withthis type of diaphragm the effective aperture of the system is obviouslydetermined by the length of the plates (i.e. their radial dimension) andby the spacing between them. This effective aperture can be madepractically equal for all points on the image surface, so that a uniformillumination of the image surface is obtained.

A shutter of the camera may, according to the invention, be constructedfor instance as a cylindrically curved vertical or horizontal slitshutter situated at the exit or entrance side for light rays of theoptical system. In some case it will be found expedient to use, insteadof this shutter, a light-tight ring or portion of a ring which ispositioned coaxially with the film carrier in the path of thelight-beams and which can be moved up and down by a driving mechanism.

In another advantageous embodiment of the camera according to theinvention a shutter is provided comprising a plurality of blades spacedat regular distances from each other in front of the entrance surface ofthe optical system, all of these blades being rotatable on spindlessubstantially parallel to the film carrier axis and further comprisingmeans whereby the shutter blades can be moved from the rest position inwhich they shut off the light from the entrance surface of the opticalsystem, to the radial position required for exposure.

The driving means may comprise, for instance, a central cog wheel or cogrim of large diameter in mesh with small cog wheels fitted to thespindles of the shutter blades.

By rotating the central cog wheel through a small predetermined angle,all the shutter blades are made to rotate through an angle of 90,thereby clearing the optical system for an exposure. The shutter bladescan then be turned back or turned forward in the same direction, so thatthe shutter is again closed. With the latter method the moving back ofthe shutter blades through an angle of over 180 to the initial positionis effected only at the next exposure. Owing to the fact that theshutter blades and the diaphragm plates described above may be similarlyshaped, whilst the diaphragm plates of course only enter into play whenthe lens is open, it is in some cases possible according to theinvention to combine the two functions into one set of blades or plates.

In the camera according to the invention it is generally desirable tomake the top and bottom end faces of the optical system rough and tolacquer them with a dull finish in order to minimize reflection of lightrays at these surfaces. The wish to have the largest possible field ofview in the vertical direction, combined with the requirements to beobserved in the manufacture of the camera lens, may result in anarrangement in which the effective light-rays brush very closely and ata very small angle along the end faces of the spherical segment. Thereflection of these light-rays may thereby have an adverse effect uponthe brilliancy of the image obtained.

According to the invention it may be found expedient under suchcircumstances to make the above-mentioned end faces concave and tocement on to them similarly shaped disks of transparent material whoseindex of refraction is equal to or differs but slightly from these ofthe materials of which the spherical segment is made. There will then bepractically no reflection at these surfaces, a feature that is conduciveto good quality of the image.

I am aware that concentric spherical systems of the kind referred to areknown in themselves. As early as 1859, in the British Patent 2,193/1859, Sutton indicated an optical system consisting of concentricspherical shells, into which a liquid was introduced.

Of more recent data is the system, likewise concentric, reproduced intheManual of Photogrammetry of the American Society of Photogrammetry, 2ndedition, Fig. 12B. The optical system of this wide-angle camera is inthe shape of a sphere formed by concentric spherical shells and twohemispherical cores and gives a concentric, spherically curved imageface. The emulsion support consists in this case of precisely groundbowlshaped glass bodies on to which the sensitive emulsion is poured.The diaphragm is positioned in the centre of the system. The manufactureof the spherical emulsion supports is difficult, whilst the handling ofthese parts during photography is cumbrous and delicate. Anotherdrawback is that no suitable shutter can be provided. For these reasonsthe system has not found acceptance. Besides, it will be understood thatthis already disclosed system is restricted for principle reasons to afield angle of less than 180.

The characteristic feature of the invention may be better understoodwhen reading the following description of some of its embodiments withreference to the drawings, in which:

FIG. 1 is a section of a so-called horizon camera with an image angle inthe horizontal direction of 360;

FIG. 2 is a section of the camera, cut in the plane IIII of FIG. 1;

FIG. 3 is a section of a modified form of the horizon camera;

FIG. 4 is a section of the camera of FIG. 3, cut in the plane IV-IV and'FIG. 5 is a section of a camera similar to that shown in FIG. 1 with amodified lens.

FIGURES 1 and 2 show schematically a camera according to the invention,which is adapted for an angular field in one direction of 360, whilstthe field in the direction perpendicular thereto is, for instance, 5.With a camera of this kind the entire horizon can be covered in onesingle shot. The camera lens is shaped essentially as a sphericalsegment and consists of two cemented portions: the spherical segment 23and the surrounding ring 24, which is part of a spherical shell. Thisoptical system is mounted in a housing 22 shaped essentially as a fiat,cylindrical box whose inner space is divided into two different levelsby an annular partition 29 which, while fitting around the sphericalsegment, has a slight conical rise towards the centre. Under the ring 29is the space through which the rays emerging from the camera lens movetowards the film 25, which is placed around the circumference in theform of a cylindrical surface. The light-rays enter along the upper sideof the ring 29, where the shutter 26 and the diaphragm 27 are situated,and are refracted downward by the optical system 23, 24 as shown in thedrawing and made to converge at the required point on the image surface,which is situated in the lower level portion of the housing.

The corresponding light-rays from diametrically opposed points of thehorizon run in the same meridional plane and therefore intersect at somepoint in the camera lens.

The outer surface of the spherical segment is divided by the ring 29into two encircling zones situated one above the other, in the upper ofwhich light enters, whilst in the lower zone the light from thediametrical opposite direction emerges from the system. By thisarrangement it is possible to produce all horizontal angular fieldsbetween and 360, it being noted that for intermediate image angles thetwo zones need not extend around the entire spherical segment but maymerely run parallel to each other through a certain angle.

The stop device in this case consists partly of radially positionedplates 27, the function of which is to limit the width of light beamsentering the camera as has been fully explained in my copendingapplication Serial No. 621,794, now Patent 2,923,220. In the embodimentshown in the drawing the same function is also performed by blades 26 ofthe shutter fitted behind the diaphragm. These blades 26 are rotatableon spindles 30 and can be actuated jointly by the release mechanism ofthe camera in a manner not shown in the drawing. For this purposes smallcog wheels on spindles 30 could e.g. cooperate with a cog wheel of largecross-section which is driven by a spindle passing through point M. Inthe drawing it has been assumed that at each exposure the shutter blades26 rotate through an angle of over 180. The blades are shown in theclosed position, the open position being indicated by dotted lines. Inthe latter position the shutter blades are lined up with thecorresponding diaphragm plates and thus may perform the same function asthe latter. It will be obvious that in certain cases the function of thefixed diaphragm plates can dur ing exposure be taken over entirely bythe shutter blades, so that separate stop plates are no longer required.For the prevention of scattered light, an opaque ring-shaped screen 28is provided.

The data for the optical system of FIGURES 1 and 2 areas follows: Theradius of curvature of the outermost surface of the spherical shell is56.4 mm., that of the inner surface 28.3 mm. The spherical shellconsists of optical glass with 11 :1648 and a dispersion factor v=34.l,whilst portion 2 is of glass with n ==1.510 and |/=63.8. The focallength is 100 mm. and the relative aperture 125.6. The field is 5 x360".

FIGURES 3 and 4 show sections of another embodiment of the horizoncamera according to the invention. The optiaol system again consists ofa portion of a spherical shell 32 and a partial spherical core 31. Thespherioal segment thus formed has a concave lower face 35 on which thedisk 36 is cemented, the function of which plate will be explainedlater. The focal length is 102. mm; the spherical shell 32 has an innerradius of 28.18 mm. and an outer radius of 56.23 mm. The film isstandard film of 36 mm. width and has a double perforation. The radiusof the lower face 35, which is shown sperical in the drawing, is 200 mm.Disk 36 is made of the same material as the spherical shell 32, viz.,glass having n=1.648 and 11:34.1. The core 31 is again of glass havingn=l.5l0 and 11:63.8.

The shutter is formed by an opaque ring 37 which drops with its loweredge into groove 37 of the partition and can be moved upward via a darkslide 38 by means of appropriate [appliances not shown in the drawing.The plates of the diaphragm are indicated as 39.

FIG. 3 shows the light beams 40 and 41 coming from the points in theobject plane (considered at infinity) which are situated on theoutermost boundaries of the vertical angular field. The total verticalfield amounts to 13.5 of which 9.5 is above the horizon and 4 below it.In cases where the aim is to obtain the largest possible field in avertical direction, this field difference above and below the horizon isdue to the presence of the cylindrical film chamber under the entrancezone of the camera lens. Whilst the field below the horizon is on thisaccount bound down to practical limits, the field above the horizon neednot for symmetrys sake be limited to the same angle. By displacing thefilm support 43 downward, the latter has been brought into such aposition that its central point is situated under the horizontal planepassing through the centre M of the camera lens. This is tantamount to afield angle above the horizon laryer than that below the horizon. It isa fortunate circumstance that this angular field difference is inaccordance with the demands that will be made upon the camera duringnormal use. The camera will practically always be mounted at acomparatively small height above the earth for taking photographs onwhich objects (buildings, trees, mountains) in an area extending aconsiderable distance from the camera are reproduced in full, whereasthe fiat foreground in the immediate environment of the camera which isof little value in a panorama does not appear on the photo.

By giving the film support a suitable construction in the shape of animage flattening lens 44, it has been ensured that the image surfacewill remain cylindrical even if the film 42 is positioned asymmetricallywith respect to the camera lens.

As can be seen from FIG. 3 the comparatively large field of the camerain a vertical direction has the efiect that the outermost beam 40 passespractically along the lower face of the spherical segment. It is notdesirable to shift this lower face further downward, as in that case thespherical shell 32 could no longer be made in one piece. As alreadymentioned, an unduly high reflection from the lower face 35 of thespherical segment has, according to the invention, been prevented by thefact that this face has been ground to a concave form and is providedwith the disk 36, cemented to it, which is made of a material havingpractically the same index of refraction. On its underside the disk isof course finished in such a way as to minimize any possible reflectionof light diffused through the system. For the sake of completeness itmay be noted that reflection-resisting disks like 36 can, if necessary,be placed against the two end faces as well or only against the upperface of the spherical segment.

FIGURES 3 and 4 reproduce schematically a special arrangement for thefilm conveyance system whereby the feed spool and the take-up spool ofthe camera are mounted underneath the optical system instead of besideit, thus permitting a very compact construction of the camera housing.In view of this the film is fed to the film carrier and removed afterexposure in spiral loops.

Item 42 in the figures is the camera housing, on one of which there isan extension 63 containing the film loops. The bottom edge of thehousing closes light-tight in a channel 49 of a bed plate 48. Joined tothis bed plate by pins 50 is a chassis plate '47, which is kept at adistance by the metal pins. Supported by these two plates 47 and 48 isthe film conveyance mechanism, consisting of the sprockets 57, 58, 57',58' and the pressure rollers 60, 61, 60', 61' bearing upon them. For thesake of clarity in the drawing the details of the pivots have beenomitted. Sprockets 57, 58 on the pulling side are rigidly mounted on thespindle 56, which is led out through the bed plate 48 and can be drivenby suitable external agencies not shown in the drawing. Thecorresponding sprockets at the feed end 57, 58' are mounted on a spindle56' which is not driven. Mounted on the spindle 59, which is pivotelymounted in spring loaded levers not shown in the drawing, are pressurerollers 60, 61, which rotate freely and which serve to prevent the filmfrom running off the sprockets. The pressure rollers 60, 61' (which arenot visible in the figure) co-operate in a similar manner with thesprockets 57', 58. Between the plates 47 and 48 are also the take-upspool 51 and the film spool 51'. The spindle 52 of the first-mentionedspool is slip-driven via a rope drive 53, 54, 55 by the sprocket shaft56, the film being thereby kept taut. The feed spool 51' rotates freelyon the spindle 52'.

The film carrier 44 is mounted on a flat, circular table 45, which at 46is pivotly mounted on to the chassis plate 47. The film 43 runs off thefeed spool 51', passes between the sprockets 57 and the pressure rollers61, after which it is formed into a loop 62' of 360 and thus becomespositioned at the same height as the film carrier of the camera. Passingbetween the sprockets 58' and the pressure rollers 60' (not visible inthe figure), the film comes into the image surface, is stretched tautaround the film carrier over an angle of nearly 360 and is finallyguided in a similar manner, by means of sprockets 57, 58 and pressurerollers 60, 61, to the take-up spool 51.

It will be clearly seen, that the rotatable mounting of the film carrier44 shown in the drawing, avoids all mutual motion between the film andfilm carrier which might cause damage to the film. After each exposurethe table 45 together with the film carrier 44 makes a completerevolution during which the exposed portion of the film is wound off thecarrier and a fresh piece of film taken up.

It goes without saying that the examples given do not exhaust thepossibilities of the invention either as regards the lens or as regardsfurther technical provisions of the camera. It should be noted inparticular that, with a view to obtaining the desired state ofcorrection, the optical system may be made up of a larger number ofelements than are shown in the drawing; it may, for instance, compriseseveral spherical shells or shell portions made of different grades ofglass. This modificaiton is illustrated in FIGURE 5, which shows acamera identical to that shown in FIGURE 1, except that the lens has aplurality of spherical shell portions 24' and 24' around the sphericalsegment 23.

What I claim is:

1. A panoramic camera having a horizontal field larger than 180,comprising, a housing having an exposure aperture therein, an opticalsystem in said housing substantially in the shape of a portion of atransparent sphere and having at least one internal refracting surfacewhich is spherical and substantially concentric with the externalsurface of said optical system, a horizontal partition in said housingwhich divides the interior thereof into an upper compartment and a lowercompartment and fits around said optical system, to thereby define afirst area of said external surface which is above said partition andserves as an entrance surface of said optical system for light raysincident through said exposure aperture, and a second area of saidexternal surface which is below said partition and serves as an exitsurface of'said optical system for light rays having traversed saidoptical system, a transparent film carrier in said lower compartmentspaced from said exit surface for carrying a strip of film on its outersurface, said outer surface being substantially cylindrical and having avertical axis passing through the common center of curvature of saidexternal and internal surfaces, and stop means in the path of the lightrays before said entrance surface for preventing such incident lightrays from entering said optical system Whose angle with a vertical planeradial to said optical system exceeds a given value.

2. A panoramic camera as claimed in claim 1, wherein said optical systemcomprises a transparent central body in the shape of a spherical segmenthaving a substantially plane bottom end face, and a portion of atransparent concentric spherical shell surrounding said central body,said spherical shell having on its outer surface said entrance and exitsurfaces of said optical system.

3. A panoramic camera as claimed in claim 1, wherein said optical systemcomprises a transparent central body in the shape of a spherical segmenthaving a substantially plane bottom end face, anda number of portions ofspherical shells, the innermost of said spherical shells surroundingsaid central body, and the outermost of said spherical shells having onits outer surface said entrance and exit surfaces of said opticalsystem.

4. A panoramic camera as claimed in claim 1, wherein there is interposedin the path of the light rays between said exit surface of said opticalsystem and the outer surface of said film carrier an annular lens havingat least one concave-toric refractive surface, whereby the 3 focalsurface of said optical system is made cylindrical.

5. A panoramic camera as claimed in claim 1, wherein said film carriercomprises a cylindrical outer surface and a refractive concave-toricinner surface.

6. A panoramic camera as claimed in claim 1, wherein said stop meanscomprises a plurality of thin, opaque, flat plates evenly distributedover said exposure aperture, said plates being in vertical planes radialto said vertical axis of said film carrier.

7. A panoramic camera as claimed in claim 6, wherein said stop platesare simultaneously rotatable about vertical axes so as to function asshutter blades.

' 8. A panoramic camera as claimed in claim 1, having a shutter in theform of a ring mounted in the path of the light rays coaxially with saidfilm support and reciprocable vertically.

9. A panoramic camera as claimed in claim 1, having a shutter comprisinga plurality of thin, opaque blades spaced at regular distances from eachother in front of said entrance surface of said optical system, saidblades being rotatably mounted on vertical spindles, and means formoving said blades from a rest position at which they shut off lightfrom the entrance surface of said optical system to the radial positionrequired for exposure.

10. A panoramic camera as claimed in claim 1, wherein said filmcarrier'is mounted in said housing for free rotation about its verticalaxis whereby during transport of said strip of film said film carrier ismade to rotate at the same circumferential speed as said strip of film.

References Cited in the file of this patent UNITED STATES PATENTS687,592 Bannell Nov. 26, 1901 FOREIGN PATENTS 2,193 Great Britain Sept.28, 1859

